Effect of distension of the gallbladder on plasma renin activity in anesthetized pigs

Background - Gallbladder pathology has been associated with cardiovascular disease. Recently, we showed that gallbladder distension in anesthetized pigs reflexly increased heart rate, arterial pressure, and coronary and renal vascular resistance through efferent sympathetic mechanisms. Renin release is affected by sympathetic output, and angiotensin liberation may result in vasoconstriction. This study was undertaken to determine whether gallbladder distension primarily causes a reflex change in plasma renin activity (PRA) and to assess its influence on observed pressor and coronary responses as well as on regional vascular resistance. Methods and Results - In 34 α-chloralose-anesthetized pigs, balloons positioned within the gallbladder were distended for 30 minutes with volumes of Ringer's solution equal to those of withdrawn bile. In 19 pigs, gallbladder distension at constant heart rate, arterial pressure, and renal flow increased PRA in the absence of changes in urinary sodium excretion. This increase was abolished by cervical vagotomy, section of renal nerves, or blockade of β- adrenergic receptors. In another 15 pigs, blockade of angiotensin II receptors significantly attenuated the pressor and coronary, mesenteric, and iliac vasoconstriction responses to gallbladder distension. Conclusions - The present study showed that innocuous gallbladder distension primarily caused a reflex increase in PRA. This increase, which involved afferent vagal pathways and efferent sympathetic mechanisms related to β-adrenergic receptors, contributed significantly to the pressor and coronary, mesenteric, and iliac vasoconstriction responses to gallbladder distension.